1. Field of the Invention
The invention relates to metering devices and, more particularly, to a liquid metering device for a gas analyzer.
2. Description of the Related Art
DE 10127353 A1 discloses a conventional a liquid metering device comprising a droplet generator.
For processing or treating liquids, for example, their analysis, prior purification of the sample of dissolved components which cannot be vaporized by complete vaporization and subsequent complete condensation of the liquid can be required. Especially in process chromatography, the metering procedure is to be process capable, i.e., able to be performed automatically. The smallest liquid quantity which can be metered is to be significantly less than 0.1 μl and discrimination of the vaporized liquid sample, for example, in the form of local concentration differences of different vaporization components in the vapor, is to be prevented. Thus, for example, simply dripping the liquid into a heated vaporization space results in uneven vaporization, because each individual droplet vaporizes in a fractionated manner in a time determined by droplet size and external circumstances. Here, ingredients having a low boiling point vaporize first and ingredients having a high boiling point vaporize last.
Therefore, in conventional liquid metering devices, a droplet generator is provided which, upon excitation, shoots a liquid droplet counter to a gas stream from a cold area into a heatable area, e.g., a capillary tube. The droplet generator has a reservoir and a displacement space which can be modified by an electromechanical transducer, e.g., a piezo transducer, and which has an outlet opening for the droplets.
Ultrasmall droplets having a volume of, for example, 50 μl may be generated using the droplet generator, which shoots the liquid in droplets at high speed. As a result, ultrasmall liquid quantities may also be precisely metered via the number of the droplets to be generated. The droplets shot into the heatable area vaporize rapidly and completely therein. Here, no discrimination of the liquid sample occurs because of the very small droplet size and the unsplit operating mode. Liquid that unintentionally swells out of the outlet opening of the droplet generator is disposed of by the gas stream and does not reach the capillary tube.